PROJECT SUMMARY This is an application for a K08 award for Dr. Sellers, an Instructor of Pediatrics at Stanford University School of Medicine. Dr. Sellers is researching ion transport in Cystic Fibrosis (CF) airway and intestine and wishes to establish himself as a young investigator in CF translational research. The K08 award for CF research on intestinal bicarbonate secretion will provide Dr. Sellers support to achieve the following goals for his career development: i) to establish patient derived 3-dimensional duodenal enteroids which recapitulate native CF duodenal tissue?s bicarbonate secretory properties, ii) to gain expertise in CRISPR/Cas9 editing techniques that can complement pharmacologic interventions to study ion transport, and iii) to gain experience in translational investigation into identifying new therapeutic modulators of duodenal bicarbonate secretion in CF. To oversee Dr. Sellers? training, he will be mentored by Dr. Calvin Kuo, an established figure in in vitro organoid models. He will also be co-mentored by Dr. Jeffrey Wine, an expert in CF ion transport. Dr. Sellers has also formed an advisory team of Dr. Matthew Porteus, Dr. Eric Sibley, and Dr. Kim Barrett, who will complement the expertise of Dr. Sellers, Kuo, and Wine, and provide additional expert oversight for Dr. Sellers? proposed research. Dr. Sellers has surrounded himself with a group of established investigators that will ensure his success. Cystic Fibrosis is the most common, life-shortening genetic disease, affecting approximately 30,000 persons in the U.S. and 100,000 persons worldwide. Lung failure remains the number one cause for mortality in CF, however, patients experience significant morbidity associated with gastrointestinal manifestations and these are known to contribute to the decline in pulmonary function. The importance of bicarbonate secretion through the cystic fibrosis transmembrane conductance regulator (CFTR) in CF has gained traction in recent years. There are newly developed drugs that improve CFTR expression and function, but there are no therapies aimed at specifically improving bicarbonate secretion, and as such an important therapeutic gap exists. To identify new ways to increase bicarbonate secretion in CF, Dr. Sellers will use developing technologies with 3-dimensional enteroid cultures and CRISPR/Cas9 editing to investigate cellular signaling pathways that promote bicarbonate transport. This project will close the gap on establishing a human-based model for investigating bicarbonate secretion in CF and will also utilize gene editing tools that can delineate signaling pathways where no specific pharmacologic tools exist. It is anticipated that this research plan will not only identify new therapeutic bicarbonate secretory pathways in CF, but together with the training plan, will enhance Dr. Sellers? transition to independence as a physician-scientist in CF translational research.